Multi-stent and multi-balloon apparatus for treating bifurcations and methods of use

ABSTRACT

A system for treating a bifurcated vessel that includes a first delivery catheter and a second delivery catheter. The first delivery catheter carries a proximal first stent and a distal second stent. The first delivery catheter also has a first elongate shaft, a proximal first expandable member with the proximal first stent disposed thereover, and a distal second expandable member with the distal second stent disposed thereover. The proximal first expandable member and distal second expandable member are independently expandable of one another. The second delivery catheter carries a third stent. The second delivery catheter also has a second elongate shaft, and a third expandable member with the third stent disposed thereover. The third expandable member is independently expandable of the proximal first expandable member and the distal second expandable member.

CROSS REFERENCE TO RELATED APPLICATION DATA

The present application is a continuation of U.S. patent applicationSer. No. 14/971,615 filed on Dec. 16, 2015 (SLW ref 5133.007US2), whichis a continuation of U.S. patent application Ser. No. 13/796,466, filedon Mar. 12, 2013 (SLW ref 5133.007US1) now U.S. Pat. No. 9,254,210,which is a continuation of PCT International Application No.PCT/US2012/024366 filed on Feb. 8, 2012 (SLW ref 5133.007WO1), which isa non-provisional of and claims the benefit of U.S. Provisional PatentApplication No. 61/440,742 filed on Feb. 8, 2011 (SLW ref 5133.007PRV);the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Angioplasty and stenting of blood vessels or other body lumens arecommonly performed today. Angioplasty is often performed by expanding aballoon in a vessel in order to reduce or eliminate plaque or otherblockages. In many cases, a stent is also implanted in the vessel inorder to further ensure a positive clinical result. A stent is animplantable scaffold that is typically delivered percutaneously anddeployed in a vein, artery, or other tubular body organ for treating anocclusion, stenosis, aneurysm, collapse, dissection, or weakened,diseased, or abnormally dilated vessel or vessel wall. The stent isradially expanded in situ, thereby expanding and/or supporting thevessel wall or body organ wall. In particular, stents are quite commonlyimplanted in the coronary, cardiac, pulmonary, neurovascular, peripheralvascular, renal, gastrointestinal and reproductive systems. Stents havealso been successfully used to reinforce other body parts, such as theurinary tract, the bile duct, the esophagus, the tracheo-bronchial treeand the brain.

Stents may improve angioplasty results by preventing elastic recoil andremodeling of the vessel wall. Stents also can be used to treatdissections in blood vessel walls that are caused by balloonangioplasty. In this situation, the stent is used to appose dissectedintimal flaps of tissue which otherwise would extend into and block avessel.

Conventional stents have also been used to treat more complex vascularproblems, such as lesions at or near bifurcation points in the vascularsystem. A bifurcation is where a secondary artery (sometimes referred toas a side branch or daughter vessel) branches out of a typically largervessel (sometimes referred to as the main branch or mother vessel).Stenting of bifurcations can present may challenges. For example, astent that traverses the ostium of the side branch may obstruct bloodflow into the side branch. Moreover, the struts in a stent may alsoblock the side branch, limiting or preventing access to the side branchby another diagnostic or therapeutic device such as another catheter.This phenomenon is commonly referred to as “stent jailing.” In stillother situations, inflation of balloons and expansion of stents in abifurcation can result in undesirable plaque shifting, which issometimes referred to as “snow plowing.” Other challenges with treatmentof a bifurcated vessel can be the result of vessel spasm, dissection,thrombosis, etc.

More recently stents and balloons have also been used to elute drugslocally to the treatment site. Drugs such as rapamycin, everolimus,biolimus A9 and other analogs of rapamycin, as well as paclitaxel arepromising in reducing restenosis rates, yet many of the aforementionedchallenges of treating a bifurcation still exist.

It would therefore be desirable to provide improved medical devices andmethods for treating bifurcated vessels. It would also be desirable toprovide improved medical devices and methods that are easier to use,safer, more reliable, and that provide a better clinical outcomecompared with currently available medical devices.

Therefore, given the challenges of current stent technology, a needexists for improved stent delivery systems and methods, particularly fortreating bifurcated vessels. At least some of these objectives will bemet by the present invention.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to methods and delivery systems used todilate and/or deliver stents in a bifurcated vessel. Embodiments may beconfigured to stent at least a portion of a mother vessel and a portionof a daughter vessel.

In a first aspect of the present invention, a system for treating apatient's bifurcated vessel having a main branch and a side branchcomprises a first delivery catheter and a second delivery catheter. Thefirst delivery catheter carries a first stent which comprises a proximalstent and a distal stent. The first delivery catheter also has a firstelongate shaft with a proximal and a distal end. A proximal expandablemember has the proximal stent disposed thereover, and a distalexpandable member has the distal stent disposed thereover. The proximaland distal expandable members are disposed adjacent the distal end ofthe first elongate shaft. The proximal and distal expandable memberseach have a collapsed configuration and a radially expandedconfiguration. The collapsed configuration has a profile suitable foradvancement through a blood vessel, and the expanded configuration has alarger profile than the collapsed configuration profile. The proximaland the distal expandable members are independently expandable of oneanother.

The second delivery catheter carries a second stent, and also has asecond elongate shaft with a proximal and a distal end. A secondexpandable member with the second stent disposed thereover is disposedadjacent the distal end of the second elongate shaft. The secondexpandable member has a collapsed configuration and a radially expandedconfiguration. The collapsed configuration has a profile suitable foradvancement through a blood vessel, and the expanded configuration has alarger profile than the profile in the collapsed configuration. Thesecond expandable member is independently expandable of the proximal andthe distal expandable members.

In another aspect of the present invention, a system for dilating abifurcated vessel having a main branch and a side branch in a patientcomprises a first delivery catheter and a second delivery catheter. Thefirst delivery catheter has a first elongate shaft with a proximal and adistal end, a proximal expandable member, and a distal expandablemember. The proximal and distal expandable members are disposed adjacentthe distal end of the first elongate shaft. The proximal and distalexpandable members each have a collapsed configuration and a radiallyexpanded configuration. The collapsed configuration has a profilesuitable for advancement through a blood vessel, and the expandedconfiguration has a larger profile than the collapsed configurationprofile. The proximal and distal expandable members are independentlyexpandable of one another.

The second delivery catheter has a second elongate shaft with a proximaland a distal end, and a second expandable member. The second expandablemember is disposed adjacent the distal end of the second elongate shaft.The second expandable member has a collapsed configuration and aradially expanded configuration. The collapsed configuration has aprofile suitable for advancement through a blood vessel, and theexpanded configuration has a larger profile than the profile in thecollapsed configuration. The second expandable member is independentlyexpandable of the proximal and the distal expandable members.

The first delivery catheter may be adapted to deliver the proximal anddistal stents to the main branch adjacent the bifurcation. The seconddelivery catheter may be adapted to deliver the second stent to the sidebranch adjacent the bifurcation. A portion of the second deliverycatheter may be disposed under a portion of the proximal stent or undera portion of the distal stent, or under a portion of both. The seconddelivery catheter may be axially slidable relative to the first deliverycatheter. The first elongate shaft may comprise a lumen which extends atleast partially between proximal and distal ends of the first elongateshaft, and the lumen may be sized to slidably receive the secondelongate shaft. The second delivery catheter may be fixed relative tothe first delivery catheter so that relative axial movement between thetwo delivery catheters is prohibited.

Each of the stents may have a collapsed configuration suitable fordelivery to the bifurcation, and a radially expanded configurationadapted to engage and support a vessel wall at the bifurcation oradjacent the bifurcation. Each of the stents may be crimped to itsrespective expandable member so as to prevent ejection of the stentduring advancement through a patient's vasculature. A proximal end ofthe distal stent in the collapsed configuration may abut a distal end ofthe proximal stent in the collapsed configuration. A proximal end of thedistal stent may abut a distal end of the proximal stent so as to form asidehole in the first stent. The proximal end of the distal stent maycomprise a notched region, and the distal end of the proximal stent mayalso comprise a notched region. The second delivery catheter mayslidably pass through the side hole in the first stent. A proximal endof the second stent may comprise a beveled section adapted to fit flushagainst a sidewall of the proximal stent or a sidewall of the distalstent. A proximal end of the second stent in the radially expandedconfiguration may be aligned with and abut a side of both the proximalstent in the radially expanded configuration and a side of the distalstent in the radially expanded configuration.

A gap may separate the proximal and the distal expandable members whenboth the proximal and the distal expandable members are in the collapsedconfiguration. The gap may be disposed between a proximal end of distalexpandable member and a distal end of the proximal expandable member.Expansion of the proximal and the distal members may displace theproximal end of the distal expandable member relative to the distal endof the proximal expandable member so that the proximal end of the distalexpandable member advances toward the distal end of the proximalexpandable member. This may decrease the gap between the proximal andthe distal expandable members. The proximal end of the distal expandablemember may abut the distal end of the proximal expandable member whenboth the proximal and the distal expandable members are in the expandedconfiguration. The proximal expandable member, the distal expandablemember, or the second expandable member may comprise a balloon. Aproximal end of the second expandable member may abut a side of both theproximal and the distal expandable members when the proximal, thedistal, and the second expandable members are in the radially expandedconfiguration.

At least one of the first elongate shaft or the second elongate shaftmay comprise a guidewire lumen extending at least partially between itsproximal and distal ends. The guidewire lumen may be sized to slidablyreceive a guidewire. The first elongate shaft may comprise a proximalguidewire port and a distal guidewire port adjacent the distal endthereof, and the proximal guidewire port may be closer to the proximalend of the first elongate shaft than the distal end of the firstelongate shaft. The proximal guidewire port may be closer to the distalguidewire port than the proximal end of the first elongate shaft. Thesecond elongate shaft may comprise a proximal guidewire port and adistal guidewire port adjacent the distal end thereof, and the proximalguidewire port may be closer to the proximal end of the second elongateshaft than the distal end of the second elongate shaft. The proximalguidewire port may be closer to the distal guidewire port than theproximal end of the second elongate shaft.

In still another aspect of the present invention, a method for treatinga bifurcated vessel having a main branch and a side branch in patientcomprises providing a first delivery catheter and a second deliverycatheter. The first delivery catheter comprises a proximal expandablemember, a distal expandable member and a first stent. The proximal anddistal expandable members are disposed near a distal end of the firstdelivery catheter. The first stent comprises a proximal stent and adistal stent. The proximal stent is disposed over the proximalexpandable member, and the distal stent is disposed over the distalexpandable member. A distal portion of the proximal stent comprises anotched region, and a proximal portion of the distal stent comprises anotched region. The two notched regions are adjacent one another to forma side hole in the first stent.

The second delivery catheter comprises a second expandable member and asecond stent. The second expandable member is disposed near a distal endof the second delivery catheter, and the second stent is disposed overthe second expandable member. The second delivery catheter passesthrough the side hole in the first stent. Advancing the first and thesecond delivery catheter positions the two catheters toward thebifurcation so that the side hole in the first stent may be aligned withthe side branch. The second stent is radially expanded from a collapsedconfiguration to an expanded configuration. The proximal stent isradially expanded from a collapsed configuration to an expandedconfiguration, and the distal stent is radially expanded from acollapsed configuration to an expanded configuration.

Advancing the first and the second delivery catheters may compriseadvancing the first delivery catheter or the second delivery catheterover a guidewire. Aligning the side hole may comprise advancing thefirst delivery catheter and the second delivery catheter until one ormore of the delivery catheters engage a carina of the bifurcation.

Radially expanding the second stent may comprise expanding the secondstent to engage a wall of the side branch or a wall of the main branch.Radially expanding the second stent may also comprise expanding thesecond expandable member. The second expandable member may comprise aballoon, and expanding the second expandable member may compriseinflating the balloon. The second stent may be radially expanded priorto radial expansion of the proximal stent or the distal stent.

Radially expanding the proximal stent may comprise expanding theproximal stent to engage a wall of the main branch. Radially expandingthe proximal stent may also comprise expanding the proximal expandablemember. The proximal expandable member may comprise a balloon, andexpanding the proximal expandable member may comprise inflating theballoon. The proximal stent may be radially expanded before radialexpansion of the distal stent.

Radially expanding the distal stent may comprise expanding the distalstent to engage a wall of the main branch or a wall of the side branch.Radially expanding the distal stent may also comprise expanding thedistal expandable member. The distal expandable member may comprise aballoon, and expanding the distal expandable member may compriseinflating the balloon.

The method may further comprise proximally retracting the seconddelivery catheter so that a proximal end of the second stent is alignedwith the side hole in the first stent. A proximal end of the secondstent may be aligned with an ostium of the side branch. Proximallyretracting the second delivery catheter may comprise aligning aradiopaque maker on the second delivery catheter with a radiopaquemarker on the first delivery catheter. Proximally retracting the seconddelivery catheter may comprise sliding the second delivery catheterunder a portion of the first stent. The second delivery catheter mayslide under a portion of the proximal stent or under a portion of thedistal stent. Proximally retracting the second delivery catheter maycomprise sliding the second delivery catheter through the side hole inthe first stent. A proximal portion of the second stent may abut both adistal portion of the proximal stent and a proximal portion of thedistal stent after radial expansion of the proximal stent, the distalstent, and the second stent. The distal portion of the proximal stentmay abut the proximal portion of the distal stent after radial expansionof the stents.

In still another aspect of the present invention, a method for treatinga bifurcated vessel having a main branch and a side branch in a patientcomprises providing a first delivery catheter and a second deliverycatheter. The first delivery catheter comprises a proximal expandablemember, a distal expandable member and a first stent. The proximal anddistal expandable members are disposed near a distal end of the firstdelivery catheter. The first stent comprises a proximal stent and adistal stent. The proximal stent is disposed over the proximalexpandable member, and the distal stent is disposed over the distalexpandable member. A distal portion of the proximal stent comprises anotched region, and a proximal portion of the distal stent comprises anotched region. The notched regions are adjacent one another to form aside hole in the first stent.

The second delivery catheter comprises a second expandable member and asecond stent. The second expandable member is disposed near a distal endof the second delivery catheter, and the second stent is disposed overthe second expandable member. The second delivery catheter passesthrough the side hole in the first stent. Advancing the first and seconddelivery catheters positions them toward the bifurcation. The firststent and the second stent are positioned at the bifurcation such thatthe proximal stent is disposed in the main branch, the distal stent isdisposed in the side branch, and the second stent is disposed in themain branch downstream of the bifurcation. The side hole in the firststent is aligned with the main branch and faces downstream of thebifurcation. The distal stent is radially expanded from a collapsedconfiguration to an expanded configuration. The proximal stent isradially expanded from a collapsed configuration to an expandedconfiguration. The second stent is radially expanded from a collapsedconfiguration to an expanded configuration.

In yet another aspect of the present invention, a method for treating abifurcated vessel having a main branch and a side branch in a patientcomprises providing a first delivery catheter and a second deliverycatheter. The first delivery catheter comprises a proximal expandablemember and a distal expandable member. The proximal and distalexpandable members are disposed near a distal end of the first deliverycatheter, and the expandable members are independently expandable fromone another. The second delivery catheter comprises a second expandablemember disposed near a distal end thereof. The first and second deliverycatheters are advanced toward the bifurcation and the second expandablemember is positioned in the side branch. The proximal and distalexpandable members are positioned in the main branch so that theproximal expandable member is at least partially upstream of thebifurcation, and the distal expandable member is at least partiallydownstream of the bifurcation. The second expandable member is radiallyexpanded from a collapsed configuration to an expanded configuration.The proximal expandable member is radially expanded from a collapsedconfiguration to an expanded configuration. The distal expandable memberis radially expanded from a collapsed configuration to an expandedconfiguration.

Radially expanding the second expandable member may comprise expandingthe second expandable member into engagement with a wall of the sidebranch or the main branch. The second expandable member may comprise aballoon, and expanding the second expandable member may compriseinflating the balloon. The second expandable member may be expandedprior to radial expansion of the proximal expandable member or thedistal expandable member.

Radially expanding the proximal expandable member may comprise expandingthe proximal expandable member to engage a wall of the main branch. Theproximal expandable member may comprise a balloon, and expanding theexpandable member may comprise inflating the balloon. The proximalexpandable member may be expanded before radial expansion of the distalexpandable member, or before expansion of the second expandable member.The proximal expandable member may also be expanded simultaneously withthe distal expandable member, the second expandable member, orsimultaneously with both.

Radially expanding the distal expandable member may comprise expandingthe distal expandable member to engage a wall of the main branch or theside branch. The distal expandable member may comprise a balloon, andexpanding the distal expandable member may comprise inflating theballoon. The distal expandable member may be expanded before expansionof the proximal expandable member or second expandable member.

The method may further comprise proximally retracting the seconddelivery catheter so that a proximal end of the second expandable memberis aligned with an ostium of the side branch. Proximally retracting thesecond delivery catheter may comprise sliding the second deliverycatheter under a portion of the proximal expandable member. Both theproximal and distal expandable members may be radially expandedsimultaneously. A proximal portion of the distal expandable member mayengage a distal portion of the proximal expandable member.

In still another aspect of the present invention, a method for treatinga bifurcated vessel having a main branch and a side branch in a patientcomprises providing a first delivery catheter and a second deliverycatheter. The first delivery catheter comprises a proximal expandablemember and a distal expandable member. The proximal and distalexpandable members are disposed near a distal end of the first deliverycatheter. The proximal and the distal expandable members areindependently expandable from one another. The second delivery cathetercomprises a second expandable member disposed near a distal end thereof.The first and second delivery catheters are advanced toward thebifurcation, and the proximal expandable member is positioned in themain branch adjacent the bifurcation. The distal expandable member ispositioned in the side branch adjacent the bifurcation. The secondexpandable member is positioned in the main branch downstream of theproximal expandable member. The distal expandable member is radiallyexpanded from a collapsed configuration to an expanded configuration.The proximal expandable member is radially expanded from a collapsedconfiguration to an expanded configuration. The second expandable memberis radially expanded from a collapsed configuration to an expandedconfiguration.

In yet another aspect of the present invention, a system for treating apatient with a trifurcated vessel having a main branch, a first sidebranch, and a second side branch comprises a first delivery catheter, asecond delivery catheter and a third delivery catheter. The firstdelivery catheter carries a first stent. The first stent comprises aproximal stent and a distal stent. The first delivery catheter also hasa proximal elongate shaft with a proximal and a distal end, and a distalelongate shaft with a proximal and distal end. The proximal elongateshaft comprises a proximal expandable member with the proximal stentdisposed thereover, and the distal elongate shaft comprises a distalexpandable member with the distal stent disposed thereover. The proximaland distal expandable members are disposed adjacent the distal end ofthe first delivery catheter. The proximal and distal expandable memberseach have a collapsed configuration and a radially expandedconfiguration. The collapsed configuration has a profile suitable foradvancement through a blood vessel, and the expanded configuration has alarger profile than the collapsed configuration profile. The proximaland distal expandable members are independently expandable of oneanother. The second delivery catheter carries a second stent, and alsohas a second elongate shaft with a proximal and a distal end, and asecond expandable member with the second stent disposed thereover. Thesecond expandable member is disposed adjacent the distal end of thesecond elongate shaft. The second expandable member has a collapsedconfiguration and a radially expanded configuration. The collapsedconfiguration has a profile suitable for advancement through a bloodvessel, and the expanded configuration has a larger profile than theprofile in the collapsed configuration. The second expandable member isindependently expandable of the proximal and the distal expandablemembers. The third delivery catheter carries a third stent. The thirddelivery catheter also has a third elongate shaft with a proximal and adistal end, and a third expandable member with the third stent disposedthereover. The third expandable member is disposed adjacent the distalend of the third elongate shaft. The third expandable member has acollapsed configuration and a radially expanded configuration. Thecollapsed configuration has a profile suitable for advancement through ablood vessel, and the expanded configuration has a larger profile thanthe profile in the collapsed configuration. The third expandable memberis independently expandable of the second expandable member, and theproximal and the distal expandable members.

These and other embodiments are described in further detail in thefollowing description related to the appended drawing figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an exemplary embodiment of a system for treating abifurcation.

FIG. 2 illustrates an exemplary embodiment of a stent delivery systemfor treating a bifurcation.

FIG. 3A illustrates a perspective view of two notched stents that form aside hole.

FIG. 3B illustrates a flat, unrolled view of the stents in FIG. 3A.

FIG. 3C illustrates a perspective view of a side hole formed by notchingone stent in a pair of adjacent stents.

FIGS. 3D-3E illustrate how various stent geometries may conform to abifurcated vessel.

FIGS. 4A-4J illustrate an exemplary method of treating a bifurcation.

FIG. 5 illustrates another exemplary method of treating a bifurcation.

FIGS. 6A-6J illustrate an exemplary method of stenting a bifurcation.

FIG. 7 illustrates another exemplary method of stenting a bifurcation.

FIG. 8 illustrates an exemplary balloon configuration.

FIGS. 9A-9B illustrate an alternative embodiment of a balloonconfiguration.

FIGS. 10A-10B illustrate an exemplary embodiment of stent deliverysystem for treating trifurcated vessels.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to medical devices and methods, and moreparticularly to stent and dilatation delivery systems for treatingbifurcated vessels having a main branch and a side branch. However, thisis not intended to be limiting, and one of skill in the art willappreciate that the devices and methods described herein may be used totreat other regions of the body.

The scientific community is slowly moving away from a main branch vs.side branch model and nomenclature. It is now well accepted that a“mother” vessel bifurcates into two “daughter vessels,” that areanatomically after the carina. The vessel that appears to be thecontinuation of the mother vessel is usually less angulated. The othervessel may be commonly referred to as the side branch, or a daughtervessel. Therefore, in this specification, the terms “main branch,”“trunk,” or “mother vessel” may be used interchangeably. Also in thisspecification, the terms “side branch vessel” and “daughter vessel” mayalso be used interchangeably. The terms “main branch stent,” “trunkstent,” or “mother stent” are interchangeable, and the term “side branchstent” is also interchangeable with the term “daughter stent.” In thecase where a main branch vessel bifurcates into two equally sizedbranches, one of the branches may still be considered to be the mainbranch or mother vessel, and the other branch may be considered a sidebranch or daughter vessel.

Systems for Treating a Bifurcation

Referring now to FIG. 1 , a system 100 for treating bifurcationscomprises a first catheter 101 and a second catheter 125. The firstcatheter includes a first elongate shaft 102 having a proximal region104 and a distal region 112. A proximal expandable member, here aballoon 108, and a distal expandable member, also a balloon 110 aredisposed near the distal region of the first catheter 101. A gap 113separates the proximal expandable member 108 from the distal expandablemember 110. The proximal expandable member is disposed on the firstelongate shaft 102, and the distal expandable member 110 is disposedover an extended portion 112 of the first shaft 102. The extendedportion 112 may be a stepped down, reduced diameter portion of the firstshaft 102, or it may be a separate shaft that is coupled with the firstshaft 102. The extended portion may also be a coextruded shaft thatextends parallel to the first shaft. The extended portion 112 may befixed relative to the first shaft 102, or it may also be slidablymovable relative to the first shaft 102. Proximal 114 a and distal 114 bradiopaque markers may be disposed adjacent the distal expandable member110 in order to allow a physician to visualize balloon location duringfluoroscopy. Similarly, proximal 129 a and distal 129 b radiopaquemarkers may be disposed adjacent the proximal balloon 108. The markersare preferably positioned at the proximal and distal working ends of therespective balloon. An inflation lumen (not illustrated) allows theballoon 110 to be inflated from the proximal end of the first catheter.A guidewire lumen 118 extends from a distal port 115 at the distal endof the extension shaft to the proximal portion of the catheter andterminates in a Y-connector 120 having two ports 122, 124 with fittingssuch as Luer fittings. The Luer fittings may be used to fluidly couplethe catheter with a balloon inflation device such as an Indeflator, asyringe, medical tubing, or other devices commonly used during acatheterization procedure. The guidewire lumen 118 is coupled with port122, and thus the first catheter may be delivered over a guidewire GWwhich slidably passes from the distal port 115, through the extendedportion 112, though the first catheter 102, and exits proximal port 122.This configuration is commonly referred to as an over-the-wireconfiguration. While not illustrated, one of skill in the art will alsoappreciate that the proximal guidewire port may also be located anywherealong the first delivery catheter, and in some preferred embodiments theproximal port 122 is located closer to the distal port 115 than theproximal end of the first catheter. This configuration is commonlyreferred to as Rx, or rapid exchange configuration. Both balloons may beinflated independently of one another, and thus balloon 108 has its owninflation lumen (not illustrated) which is passes through the firstelongate shaft 102 and terminates at hub 116 which has a fitting such aLuer fitting to allow an inflation device such as an Indeflator to befluidly coupled to the catheter. Both the proximal and distal expandablemembers may be expanded from a collapsed configuration having a lowprofile suitable for intravascular delivery to a target treatment sitesuch as a bifurcated vessel, to a radially expanded configuration inwhich the balloons engage the walls of the target treatment site, suchas a blood vessel wall.

The second catheter 125 also has an elongate shaft 126 having a proximalportion and a distal portion. An expandable member 134, here a balloon,is disposed on the elongate shaft 126, near it's distal end. A proximal136 a and distal 136 b radiopaque marker may be coupled to the shaft 126and aligned with the balloon 134 so that a physician may visualize theballoon under fluoroscopy. The radiopaque markers 136 a, 136 b arepreferably located at the proximal and the distal working ends of theballoon 134. A proximal connector 130 is coupled to the proximal end ofthe shaft 126 and allows a syringe, inflation device, medical tubing, orother device to be fluidly coupled with an inflation lumen (not shown)which extends along the elongate shaft 126 and is fluidly coupled to theexpandable member 134. A guidewire lumen 128 extends from a distal port135 to a proximal port 132. In preferred embodiments, the proximal port132 is closer to the distal port 135 than the proximal end of theelongate shaft 126. This configuration is often referred to as Rx orrapid exchange. The guidewire lumen may also optionally extend out theproximal end of the shaft to provide a catheter having what is commonlyreferred to as an over-the-wire configuration. In preferred embodiments,shaft 126 may extend slidably through a lumen 106 in the shaft 102 ofthe first catheter 101 so that the balloon 134 may be advanced orretracted relative to the distal balloon 110. In other embodiments,shaft 126 may be fixedly attached to shaft 102 with no relative movementbetween the two catheters. Balloon 134 may be expanded from a collapsedconfiguration having a low profile suitable for intravascular deliveryto a target treatment site such as a bifurcated vessel, to a radiallyexpanded configuration in which the balloons engage the walls of thetarget treatment site, such as a blood vessel wall. Any of the balloons108, 110, 134 may be compliant, non-compliant, or semi-compliant.Moreover, any of the balloons 108, 110, 134 may have a substantiallyconstant diameter, or they may be tapered to match the contours of avessel. In preferred embodiments, the balloons are tapered andnon-compliant.

FIG. 2 illustrates another catheter system 200 for treating abifurcation. In this exemplary embodiment, catheter system 200 issimilar to the system 100 of FIG. 1 , with the major difference beingthat system 100 also includes three stents 152, 154, 158.

The first catheter carries a first stent which is comprised of twodiscrete stents, a proximal stent 152 is disposed over the proximalballoon 108 on the first catheter 101, and a distal stent 154 isdisposed over the distal balloon 110. A proximal end of the distal stent154 abuts with a distal end of the proximal stent 108. The abutting endsof the two stents are formed so that when the two stents abut oneanother, a side hole 156 is created, allowing the second elongate shaft126 to pass therethrough. Exemplary embodiments of the stent side holeare disclosed in greater detail below. The side hole 156 is preferablydisposed about midway between the proximal and distal stents 152, 154,however, by changing stent lengths or by further modifying the abuttingends of the stents, the side hole may be disposed anywhere between theends of the two stents 152, 154. A second stent 158, comprised of asingle stent is disposed over balloon 134 on the second deliverycatheter. Other aspects of delivery system 200 generally take the sameform as those previously described above with respect to catheter system100. The stents 152, 154, 158 are preferably balloon expandable, but mayalso be self-expanding, or combinations of balloon expandable andself-expanding. The stents 152, 154, 158 are radially expandable from acollapsed or crimped configuration having a profile adapted forintravascular delivery through a vessel, to an expanded configuration inwhich the stents engage and provide support for a target tissue such asa vessel wall. The stents may have any length, and in preferredembodiments, the proximal stent 152, and the distal stent 154 aresubstantially the same length. One of skill in the art will appreciatethat this is not intended to be limiting, and stent length is dependentupon the length of the target tissue being treated.

FIG. 3A illustrates a perspective view of the two stents 152, 154 inFIG. 2 , with the delivery catheter removed for clarity. A proximalportion of distal stent 154 includes a notched region 154 a, andsimilarly a distal portion of the proximal stent 152 also includes anotched portion 152 a. The notched regions may be sized so that when theproximal portion of stent 154 abuts with the distal portion of stent152, the two notched regions form a side hole 156 through which thesecond catheter 126 may pass. FIG. 3B illustrates the stents 152, 154 inthe unrolled, flattened configuration to more clearly illustrate how thenotched region may be cut into the stent. In this exemplary embodiment,the notched region is half of an ellipse, but in other embodiments, thenotched region may be circular, rectangular, or other shapes may beemployed. Also, in still other embodiments, the notch may be cut out ofonly one of the two abutting stents. FIG. 3C illustrates an exemplaryembodiment of two stents 152, 154 that form a side hole 156 when the twostents abut one another. In this embodiment, a single notch 154 a is cutout of only one of the stents, here stent 154 in this embodiment,although the notch could also be cut out of stent 152.

For conventional cylindrical stents 175 having orthogonal ends,placement in a side branch may result in a region 178 of the side branchthat is remains unscaffolded, as seen in FIG. 3D. Providing a stent 180having a beveled end 182 may allow the stent to more accurately conformto the side branch anatomy, thereby providing more uniform scaffoldingas seen in FIG. 3E.

Methods of Treating a Bifurcation

FIGS. 4A-4J illustrate an exemplary method of treating a bifurcatedvessel using the system 100 of FIG. 1 . FIG. 4A illustrates the basicanatomy of stenotic lesion at a bifurcated vessel. The blood vessel BVincludes a main branch MB and a side branch SB. At the bifurcation B,the vessel bifurcates into the side branch SB and a downstream portionof the main branch MB. The carina C is a keel-shaped ridge, process, oranatomical part of the bifurcation. A stenotic lesion L such as plaque,calcified deposits, or other narrowing material is disposed in the sidebranch, as well as in the main branch upstream and downstream of thebifurcation. The ostium O is the opening from the main branch MB intothe side branch SB.

In FIG. 4B a guidecatheter or introducer catheter IC is introduced intothe patient's vasculature, preferably percutaneously, or via cutdown.The introducer catheter IC is then advanced toward the target treatmentarea at the bifurcation. Two guidewires GW are then advanced through theintroducer catheter. One guidewire is further advanced into the sidebranch SB past the side branch lesion L, and the other guidewire isadvanced further into the main branch downstream of the main branchlesion L.

FIG. 4C shows the bifurcation treatment system 100 of FIG. 1 beingadvanced through the introducer catheter IC, over both guidewires GW.Both catheters 101, 125 are advanced distally until they engage thecarina C, resisting further distal advancement. Both catheters may beadvanced slightly distally, or retracted slightly proximally such thatthe first catheter 101 is positioned in the main branch MB with theproximal balloon 108 at least partially upstream of the bifurcation B,and the distal balloon 110 is at least partially downstream of thebifurcation B. Both balloons 108, 110 of course will be aligned with thelesion L in the main branch MB. The second catheter 125 is positioned inthe side branch SB, preferably such that balloon 134 is slightly distalto the side branch lesion L.

FIG. 4D illustrates an optional step wherein the second catheter 125 isproximally retracted through a lumen (not shown) in the first catheter101 so that proximal radiopaque marker 136 a on the second catheter 125is aligned with proximal radiopaque marker 129 a on the first catheter101. This may be seen in the partial cutaway in FIG. 4D. Thus, a portionof shaft 126 slides under proximal balloon 108 and through the shaft 102of the first catheter 101. Furthermore, this ensures alignment ofballoon 134 with the side branch lesion L, with the ostium of the sidebranch, and with the proximal 108 and distal 110 balloons. This aspectof the procedure, as well as any other aspect of the procedure may bevisualized using fluoroscopy, ultrasound, or other imaging techniquessuitable for catheterization procedures.

Once the balloons on both catheters are properly aligned with thelesion, the bifurcation, and with one another, the balloons may beradially expanded in any order in order to treat the lesion L. FIG. 4Eillustrates a preferred first inflation wherein the balloon 134 on thesecond catheter 125 is expanded against the lesion L in the side branchSB. The balloon 134 may be inflated with saline, contrast media,combinations thereof, or with other fluids. The balloons are inflated toa pressure high enough to compact the plaque into the vessel wall,preferably greater than 10 atmospheres, more preferably 10 to 20atmospheres, and even more preferably 15 to 25 atmospheres. Of course,one of skill in the art will appreciate that this pressure is notlimiting, and a physician may inflate the balloon to any desiredpressure. After the balloon is inflated once, or twice, or more, it isdeflated, and the plaque will be substantially reduced since it ispressed into the vessel wall, thereby reducing the stenotic lesion L.

FIG. 4F illustrates another preferred step, wherein the proximal balloon108 is expanded next, after expansion of the balloon 134 in the sidebranch SB. The proximal balloon may be inflated with similar fluids andpressures as previously described above. This reduces the plaque in themain branch near the bifurcation, and upstream of the bifurcation. FIG.4G illustrates the next preferred step wherein the distal balloon 110 isexpanded using similar fluids and pressures as described above.Expansion of both proximal 108 and distal 110 balloons is a modified“kissing” balloon technique. Even though the balloons 108, 110 areseparated by a gap, after inflation, the proximal end of the distalballoon 110 expands toward and abuts the distal end of the proximalballoon 108 which also advances toward the other balloon. Additionaldetails on this are disclosed below in FIGS. 8 and 9A-9B. Expanding boththe proximal and distal balloons 108, 110 ensures that the lesion L inthe main branch, both upstream and downstream of the bifurcation isuniformly dilated. Optionally, the side branch balloon 134 may also besimultaneously expanded (not illustrated) so that all three balloons“kiss” one another.

After the lesion has been successfully dilated, both proximal and distalballoons 108, 110 (and side branch balloon 134, if also expanded) aredeflated as illustrated in FIG. 4H. In FIG. 4I, both catheters 101, 125are proximally retracted away from the bifurcation, and removed from thepatient's body. Finally, in FIG. 4J, both guidewires GW and theintroducer guidecatheter 1C are also proximally retracted away from thebifurcation and removed from the patient's body. The blockage in thelumen is now substantially reduced, thereby improving blood flow acrossthe bifurcation.

The exemplary method described above is not intended to be limiting. Oneof skill in the art will appreciate that a number of variations orchanges may also be made. For example, any one or more of the balloonsmay be coated with a therapeutic agent such as an anti-restenosis druglike rapamycin, everolimus, biolimus A9, other analogs of rapamycin, orpaclitaxel to help reduce restenosis. Moreover, any order or combinationof balloon inflation may also be used. For example, the proximal anddistal balloons may be expanded prior to expansion of the side branchballoon, or the distal balloon maybe inflated before the proximalballoon. Other variations may include simultaneous inflation of the sidebranch balloon with the proximal balloon, or simultaneous inflation ofthe side branch balloon and the distal balloon. Any number ofpermutations are contemplated.

Additionally, in an alternative embodiment shown in FIG. 5 , the distalballoon 110 of the first catheter 101 may be advanced into the sidebranch SB while the proximal balloon 108 remains in the main branch MB.The balloon 134 on the second catheter 125 may then be advanced into themain MB branch at least partially downstream of the bifurcation.Inflation of the balloons may follow any of the number of permutationsdiscussed above.

FIGS. 6A-6J illustrate an exemplary method of stenting a bifurcationusing the delivery system 200 previously described in FIG. 2 above. FIG.6A illustrates the basic anatomy of stenotic lesion at a bifurcatedvessel. The blood vessel BV includes a main branch MB and a side branchSB. At the bifurcation B, the vessel bifurcates into the side branch SBand a downstream portion of the main branch MB. The carina C is akeel-shaped ridge, process, or anatomical part of the bifurcation. Astenotic lesion L such as plaque, calcified deposits, or other narrowingmaterial is disposed in the side branch, as well as in the main branchupstream and downstream of the bifurcation. The ostium O is the openingfrom the main branch MB into the side branch SB.

In FIG. 6B a guidecatheter or introducer catheter IC is introduced intothe patient's vasculature, preferably percutaneously, or via cutdown.The introducer catheter IC is then advanced toward the target treatmentarea at the bifurcation. Two guidewires GW are then advanced through theintroducer catheter. One guidewire is further advanced into the sidebranch SB past the side branch lesion L, and the other guidewire isadvanced further into the main branch downstream of the main branchlesion L.

FIG. 6C shows the bifurcation treatment system 200 of FIG. 2 beingadvanced through the introducer catheter IC, over both guidewires GW.Both catheters 101, 125 are advanced distally until they engage thecarina C, resisting further distal advancement. Both catheters may beadvanced slightly distally, or retracted slightly proximally such thatthe first catheter 101 is positioned in the main branch MB with theproximal stent 152 at least partially upstream of the bifurcation B, andthe distal stent 154 is at least partially downstream of the bifurcationB. Both stents 152, 154 of course will be aligned with the lesion L inthe main branch MB. Furthermore, the notched regions 152 a, 154 aforming the side hole 156 will also be aligned with the ostium to theside branch. The second catheter 125 is positioned in the side branchSB, preferably such that stent 158 is slightly distal to the side branchlesion L. In this embodiment, the stents 152, 154, 158 are preferablyballoon expandable. However, they may also be self-expanding, orcombinations of balloon expandable and self-expanding.

FIG. 6D illustrates an optional step wherein the second catheter 125 isproximally retracted through a lumen (not shown) in the first catheter101 so that proximal radiopaque marker 136 a on the second catheter 125is aligned with proximal radiopaque marker 129 a on the first catheter101. This may be seen in the partial cutaway in FIG. 6D. Thus, a portionof shaft 126 slides under proximal balloon 108, under proximal stent152, and through the shaft 102 of the first catheter 101. Furthermore,this ensures alignment of stent 158 with the side branch lesion L, withthe ostium of the side branch, and with the proximal 152 and distal 154balloons. This aspect of the procedure, as well as any other aspect ofthe procedure may be visualized using fluoroscopy, ultrasound, or otherimaging techniques suitable for catheterization procedures.

Once the stents on both catheters are properly aligned with the lesion,the bifurcation, and with one another, the balloons may be radiallyexpanded thereby expanding the stents to treat the lesion. FIG. 6Eillustrates a preferred first inflation wherein the balloon 134 on thesecond catheter 125 is expanded, thereby expanding stent 158 into thelesion L in the side branch SB. The balloon 134 may be inflated withsaline, contrast media, combinations thereof, or with other fluids. Theballoons are inflated to similar pressures as those previously describedabove. Of course, one of skill in the art will appreciate that thesepressures are not limiting, and a physician may inflate the balloon toany desired pressure. After the stent is expanded into the lesion, theballoon 134 is deflated. A second post-dilation may also be performed ifnecessary to further tack the stent into position.

FIG. 6F illustrates another preferred step, wherein the proximal balloon108 is expanded next so as to radially expand the proximal stent 152into the lesion L around the lesion and slightly upstream of thebifurcation. Expansion of stent 152 is performed after expansion ofstent 158 in the side branch SB. The proximal balloon may be inflatedwith similar fluids and pressures as previously described above. FIG. 6Gillustrates the next preferred step wherein the distal balloon 110 isexpanded using similar fluids and pressures as described above, therebyexpanding distal stent 154. The distal balloon is inflated while theproximal balloon is inflated. Expansion of both proximal 108 and distal110 balloons is a modified “kissing” balloon technique. Even though theballoons 108, 110 are separated by a gap, after inflation, the proximalend of the distal balloon 110 expands toward and abuts the distal end ofthe proximal balloon 108 which also advances toward the other balloon.Additional details on this are disclosed below in reference to FIGS. 8,and 9A-9B. This helps ensure that the distal end of the proximal stent152 abuts the proximal end of the distal stent 154, and that the sidehole 156 abuts the proximal end of the side branch stent 158, therebyensuring that the stent fully covers and scaffolds the bifurcation.Additionally, expanding both the proximal and distal balloons 108, 110ensures that the proximal and distal stents 152, 154 are expandeduniformly in the main branch, both upstream and downstream of thebifurcation. Optionally, the side branch balloon 134 may also besimultaneously expanded (not illustrated) so that all three balloons“kiss” with one another.

After the lesion has been successfully stented, both proximal and distalballoons 108, 110 (and side branch balloon 134, if also expanded) aredeflated as illustrated in FIG. 6H. In FIG. 6I, both catheters 101, 125are proximally retracted away from the bifurcation, and removed from thepatient's body. Finally, in FIG. 6J, both guidewires GW and theintroducer guidecatheter IC are also proximally retracted away from thebifurcation and removed from the patient's body. The blockage in thelumen is now substantially reduced and scaffolded, thereby improvingblood flow across the bifurcation.

The exemplary method described above is not intended to be limiting. Oneof skill in the art will appreciate that a number of variations orchanges may also be made. For example, any one or more of the balloons,stents, or combinations of balloons/stents may be coated with atherapeutic agent such as an anti-restenosis drug like rapamycin,everolimus, biolimus A9, other analogs of rapamycin, or paclitaxel tohelp reduce restenosis. Moreover, any order or combination ofballoon/stent expansion may be employed. For example, the proximal anddistal balloons/stents may be expanded prior to expansion of the sidebranch balloon/stent, or the distal balloon/stent maybe inflated beforethe proximal balloon/stent. Other variations may include simultaneousexpansion of the side branch balloon/stent with the proximalballoon/stent, or simultaneous inflation of the side branchballoon/stent and the distal balloon/stent. Any number of permutationsare contemplated.

Additionally, in an alternative embodiment shown in FIG. 7 , the distalstent 154 of the first catheter 101 may be advanced into the side branchSB while the proximal stent 152 remains in the main branch MB. The stent158 on the second catheter 125 may then be advanced into the main MBbranch at least partially downstream of the bifurcation. Inflation ofthe balloons may follow any of the number of permutations discussedabove.

Exemplary Balloon Configurations

FIG. 8 illustrates one exemplary balloon configuration that may be usedin any of the systems or method described above. Catheter shaft 302includes a proximal balloon 304 and a distal balloon 306 coupled to theshaft 302. Both proximal and distal balloons 304, 306 have standardproximal tapers 308 and distal tapers 310. The tapered regions 308, 310allow the balloon to be fixedly coupled to shaft 302 with a fluid tightseal. This may be accomplished by ultrasonic welding, adhesivelybonding, suture wrapping, or other techniques known to those in the art.While this configuration is promising, the gap 308 separating theproximal and distal balloons 304, 306 will remain even after bothballoons are inflated. Thus, a section of the vessel may remainundilated, or unstented, which is not optimal.

FIG. 9A illustrates another exemplary balloon configuration that mayovercome some of the shortcomings of the previous embodiment. Shaft 302includes a proximal balloon 304 a and a distal balloon 306 a. Theproximal end 312 a and the distal end 314 a of each balloon is evertedand attached to the shaft using similar techniques as those describedabove. In the unexpanded configuration of FIG. 9A, a gap 308 stillexists when the balloons are uninflated. However, when both balloons 304a, 306 a are inflated, because of the everted ends, the proximal end ofeach balloon will tend to move proximally, and the distal end of eachballoon will also tend to move distally, as indicated by the arrows.Thus, the distal end of the proximal balloon 304 a will move toward andabut the proximal end of the distal balloon 306 a. This reduces oreliminates the gap 308 between the two balloons. Therefore, the vesselwill be more uniformly dilated or stented. Also, in the case wherestents are mounted over the balloons, the ends of the stents will alsotend to move toward one another, therefore the gap between adjacentstents will also tend to close resulting in more uniform stenting.

Exemplary Stent Delivery Systems for Treating Trifucations

The embodiments described above are preferably used to treat bifurcatedvessels. However, the basic embodiment may be expanded upon in order totreat trifurcated vessels such that those with a main branch and twoside branches. FIGS. 10A-10B illustrate one exemplary embodiment of astent delivery system that may be used to stent a trifurcated vessel.Stent delivery system 1002 includes a first side branch stent deliverycatheter 1004 and a second side branch stent delivery catheter 1006.Also, the main branch stent delivery catheter includes a proximalballoon 1012 with a stent 1010 disposed thereover, and a distal balloonwith a stent 1018 disposed thereover and coupled to a central shaft1008. The central shaft includes at least three lumens sized toaccommodate the shafts of the first and second side branch catheters,and the main branch shaft. The shafts may be slidable disposed in thelumens, or they may be fixed. The first side branch stent deliverycatheter includes a balloon 1030 and stent 1031 disposed thereover nearthe catheter distal end. It is disposed in a rapid exchange lumen of themain shaft such that the proximal port 1026 is closer to the distal endof the catheter than the proximal end of the catheter. The second sidebranch catheter is similarly configured and includes a balloon 1032 anda stent 1033 disposed thereover adjacent the distal end of the catheter.The second side branch catheter is disposed in a rapid exchange lumen ofthe main shaft such that the proximal port is closer to the distal endof the catheter than the proximal end. The main branch cathteterincludes proximal balloon 1012 having a proximal taper 1016 and a distaleverted end 1014 that allows the distal end of the balloon to expanddistally toward the distal main branch balloon upon inflation. Inalternative embodiments, both ends of balloon 1012 may be tapered,everted, or the eproxima end may be everted and the distal end may betapered. The distal main branch balloon preferably includes a distaltaper 1020 and a proximal everted end 1022 that moves proximally towardthe proximal main branch balloon upon inflation. A gap 1034 separatesthe proximal main branch stent from the distal main branch stent,thereby creating a space for the first and second side branch cathetersto extend therepast. The gap may be created with the notches or otherstent geometries previously described above, with the exception that twonotches are required to form two gaps. During delivery, the two sidebranch catheters may be slidably disposed in the lumens of the mainbranch catheter. Upon reaching the target trifurcated vessel, the twoside branch catheters may be distally extended from the lumens andexposed, passing through the gap 1034 between the proximal and distalmain branch stents. The balloons may be independently inflatable therebyallowing inflation in any order to deploy stents upstream and downstreamof the trifurcation, and in the two sidebranches. Kissing balloons mayalso be used. In an alternative embodiments, one or more of the balloonsmay not include a stent, and thus the a portion of the trifurcation maybe dilated and a portion of the trifurcation may be stented.

While the above is a complete description of the preferred embodimentsof the invention, various alternatives, modifications, and equivalentsmay be used. Therefore, the above description should not be taken aslimiting the scope of the invention which is defined by the appendedclaims.

1. A system for treating a trifurcated vessel, said system comprising: afirst main elongate shaft having a proximal end, a distal end, a firstmain expandable member adjacent the distal end thereof, and a first mainstent disposed on the first main expandable member; a second mainelongate shaft having a proximal end, a distal end, a second mainexpandable member adjacent the distal end thereof, and a second mainstent disposed on the second main expandable member, wherein the secondmain elongate shaft is disposed in the first main elongate shaft; afirst side branch elongate shaft having a proximal end, a distal end, afirst side branch expandable member adjacent the distal end thereof, anda first side branch stent disposed on the first expandable member,wherein the first side branch elongate shaft is disposed in the firstmain elongate shaft; and a second side branch elongate shaft having aproximal end, a distal end, a second side branch expandable memberadjacent the distal end thereof, and a second side branch stent disposedon the second expandable member, wherein the second side branch elongateshaft is disposed in the first main elongate shaft.
 2. The system ofclaim 1, wherein the second main elongate shaft is slidably disposed inthe first main elongate shaft.
 3. The system of claim 1, wherein thefirst side branch elongate shaft is slidably disposed in the first mainelongate shaft, wherein slidable advancement of the first side branchelongate shaft advances the first side branch stent out of the firstmain elongate shaft and advances the first side branch stent between thefirst main stent and the second main stent.
 4. The system of claim 1,wherein the second side branch elongate shaft is slidably disposed inthe first main elongate shaft, wherein slidable advancement of thesecond side branch elongate shaft advances the second side branch stentout of the first main elongate shaft and advances the second side branchstent between the first main stent and the second main stent.
 5. Thesystem of claim 1, wherein one or more of the first main expandablemember, second main expandable member, first side branch expandablemember, and second side branch expandable member is a balloon.
 6. Thesystem of claim 1, wherein the first main elongate shaft comprises afirst lumen extending therethrough, and wherein the second main elongateshaft is slidably disposed in the first lumen.
 7. The system of claim 6,wherein the first main elongate shaft comprises a second lumen extendingtherethrough, and wherein the first side branch elongate shaft isslidably disposed in the second lumen.
 8. The system of claim 7, whereinthe first main elongate shaft comprises a third lumen extendingtherethrough, and wherein the second side branch elongate shaft isslidably disposed in the third lumen.
 9. The system of claim 1, whereinthe second main expandable member is distal of the first main expandablemember.
 10. The system of claim 1, wherein one or more of the secondelongate main shaft, the first side branch elongate shaft, and thesecond side branch elongate shaft are fixed relative to the first mainelongate shaft.